The Human Craniofacial Genetics Section laboratory was established in April 2004 to study the genetic basis of oral and craniofacial diseases. The goal of the section is to understand the genetic basis of human dental and craniofacial diseases so that we may identify specific etiologic components of disease that permit development of better diagnostic and treatment strategies. The laboratory is aligned along three general anatomical themes bone, teeth and skin. Investigators have been recruited whose interests and areas of expertise can be applied to each theme, with specific expertise in cell culture, immunohistochemistry and imaging, molecular biology, expression profiling of oral microbes and proteomics. The working paradigm of the section is that there is a genetic basis to human disease and that understanding the genetic basis of disease will foster development of better diagnostic and treatment strategies. Studies of genetic diseases can provide significant insight into normal as well as abnormal development. In terms of genetics, diseases can be divided into two broad types, those for which single genes are deterministic of disease, and those for which genetic factors contribute to risk, but are not individually deterministic. We are studying both simple Mendelian diseases (amelogenesis imperfecta, tricho-dento-osseous syndrome, Papillon Lefevre and hereditary gingival overgrowth), as well as complex diseases (oral facial clefting, periodontitis, Sjogrens syndrome). Gene-environment interactions are also important determinants of disease etiology. We are investigating microbial-protein interactions in the oral cavity in several diseases including dental caries, and in several conditions including pre and post bone marrow transplant and critical care patients. Genetic mutations are responsible for a number of diseases that affect the teeth and supporting tissues (gingiva, bone). Identification of the specific gene and associated mutation responsible for these diseases can provide an important starting point to understand disease. In studies of families we have identified the genes responsible for several forms of amelogenesis imperfecta. We have identified several ENAMELIN gene mutations that are responsible for nonsyndromic autosomal recessive amelogenesis imperfecta (AI). Geneotype-phenotype studies reveal a gene dosage effect of several specific ENAM mutations (e.g. g.13185_13186insAG mutation and g.12946_12947insAGTCAGTACCAGTACTGTGTC mutation), resulting in a phenotype ranging from localized enamel pitting to generalized hypoplastic AI associated with malocclusion due to a skeletal class II and open bite. Genetic studies have also identified the first known human mutation in the KLK4 gene (Kallikrein). This gene mutation is responsible for non-syndromic autosomal recessive AI. Ongoing studies are continuing to identify additional ENAM and KLK4 gene mutations responsible for AI. We have also identified the first mutations in the MMP20 gene which results in autosomal recessive amelogenesis imperfecta. The protein products of these mutated genes are being studies to characterize how each specific mutation alters proteolysis cleavage products important in enamel development. These disease states are being studied to develop a better understanding of normal and abnormal enamel development. This work is also facilitating an improved nosology for AI, which should help development of better diagnostic strategies. Cell culture studies can provide important information about the biological pathways disrupted in genetic diseases. This understanding can lead to improved clinical management of disease. We are using this approach to identify the specific biological pathways disrupted by mutation in the SOS1 gene causing gingival overgrowth and by the cathepsin C gene responsible for Papillon Lefevre syndrome. Understanding the specific mechanism by which gingival proliferation occurs in HGF may have applications for tissue engineering approaches to repair gingival defects. Ongoing studies of hereditary ginigval overgrowth are permitting us to identify expression of specific proteins in the cell cycle that are altered in gingival overgrowth. Studies of cathepsin C mutations have revealed inactivity of the protein product of this gene has a cascade effect that results in the failure to activate downstream proteins. Understanding this pathway may permit targeted intervention to stop alveolar bone resorption, providing therapeutic opportunities for treatment of periodontal diseases. Animal models of human diseases can provide a robust environment to characterize the biological properties of a mutation important for human disease. We have made constructs for a transgenic mouse with a DLX3 mutation that has beneficial gain of function properties in humans. Studying a DLX3 transgenic mouse model may provide insights that permit a better understanding of how to promote stronger bones. In vitro studies of the DLX3 mutant gene have permitted us to begin toi understand how the mutant DLX3 protein drives osteoblasts. In contrast to rare Mendelian diseases, complex genetic diseases affect significant numbers of people, but are more difficult to study. We are working to develop biomarkers with diagnostic and prognostic value for several complex genetic disease conditions. We are developing salivary diagnostic strategies to identify protein patterns as well as specific proteins that are of diagnostic value (Sjogrens syndrome) and prognostic value (Graft versus host disease following bone marrow transplant). Approaches include use of mass spectrometry to screen for identification of protein patterns of diagnostic value for disease states as well as 2 D gel separation of proteins to identify specific biomarkers. Using these high throughput proteomic appraoches, we have begun to identify salivary protein biomarkers. Gene knockout studies have determined PDGF-C is required in cleft palate formation. We have identified a specific regulatory region domain mutation in the human PDGF-C gene that is associated with cleft lip/palate in certain human populations. This mutation is associated with a decreased expression of the human gene. We are extending these studies to determine the prevalence of this SNP polymorphism in control populations and in individuals affected with CL+/P. It is believed CL+/P is genetically complex, and that gene ?environment interactions are important. Identification of specific genetic alterations that impart risk will be necessary to develop a more complete understanding of the molecular events that underlie susceptibility to this condition, providing the basis for development of improved diagnostic and treatment tools. Validation of a role for this SNP in some clefting populations will provide such information. An important goal of the sections work is development of new treatments. Identification of gene mutations responsible for disease is a first step to understanding the disease pathogenesis at the cellular and molecular levels. We are studying uromodulin associated diseases to understand endoplasmic reticulum storage diseases. Our studies have determined that mutations in the human uromodulin disease gene result in accumulation if the abnormal protein product in the endoplasmic reticulum, resulting in increased apoptosis of the epithelium lining the tubules. Since establishing the key cellular and molecular components of disease pathogenesis related to this genetic disease, we are evaluating the ability of several chemical chaperones to aid in the removal of this mutant protein from the endoplasmic reticulum, reducing apoptosis, and preserving the epithelial lining cells. We believe this model will provide the framework to develop treatments for endoplasmic reticulum storage diseases.